python - 在numpy数组中获取具有最小长度的相同条目的序列范围

Question

考虑一个数组，其条目仅由 -1 或 1 组成。如何获取所有仅包含 1 且最小长度为 t 的切片的范围(例如 t=3)

例子:

>>>a=np.array([-1,-1,1,1,1,1,1,-1,1,-1,-1,1,1,1,1], dtype=int)
>>> a
array([-1, -1,  1,  1,  1,  1,  1, -1,  1, -1, -1,  1,  1,  1,  1])

然后，t=3 所需的输出将是 [(2,7),(11,15)]。

Answer 1

一种使用 np.diff 的方法和 np.where -

# Append with `-1s` at either ends and get the differentiation
dfa = np.diff(np.hstack((-1,a,-1)))

# Get the positions of starts and stops of 1s in `a`
starts = np.where(dfa==2)[0]
stops = np.where(dfa==-2)[0]

# Get valid mask for pairs from starts and stops being of at least 3 in length
valid_mask = (stops - starts) >= 3

# Finally collect the valid pairs as the output
out = np.column_stack((starts,stops))[valid_mask].tolist()